Fuel cell has been presented as a substitute for fossil fuel. In the fuel cell, fuel including hydrogen is continually supplied, simultaneously air including oxygen is continually supplied, the hydrogen and the oxygen pass electrochemical reaction, and accordingly energy difference between before and after the reaction is directly converted into electric energy.
Fuel cells can be classified into various kinds according to kinds of fuel, operational temperature and catalyst, etc.
FIGS. 1 and 2 illustrate an example of the fuel cell. As depicted in FIGS. 1 and 2, in the fuel cell, a MEA (membrane electrode assembly) 200 is inserted between a pair of bipolar plates 100. Open grooves 110, 120 in which a fluid flows are respectively formed on both sides or a side of the bipolar plate 100. Inflow paths 130, 140 and outflow paths 150, 160 for making the fluid flow into/out of the open grooves 110, 120 are respectively formed on both sides of the bipolar plate 100. In the MEA 200, a fuel electrode (anode) 220 contacted to fuel is formed on a side of an electrolyte membrane 210 having a certain area, and an air electrode (cathode) 230 contacted to air is formed on the other side of the electrolyte membrane 210.
With the open grooves 110, 120, a fuel path in which fuel flows and an air path in which air flows are respectively formed on both sides of the MEA 200. Herein, the fuel electrode 220 is arranged on the fuel side open groove 410, 110, and the air electrode 230 is arranged on the air side open groove 420, 120.
In the above-described fuel cell, when fuel flows into the inflow path 130 of the bipolar plate 100, simultaneously air flows into the inflow path 140 of the other bipolar plate 100. The fuel in the inflow path 130 flows through the open groove 110 and is discharged through the outflow path 150. The air in the inflow path 140 flows through the open groove 120 and is discharged through the outflow path 160. The fuel discharged through the outflow path 150 flows into the inflow path 130 by an additional device and is circulated.
In the process for making the fuel flow in the open groove 110, electrochemical oxidation reaction occurs on the fuel electrode 220 of the MEA 200 contacted to the open groove 110, the hydrogen ions are moved to the air electrode 230 through the electrolyte membrane 210, and the electrons are moved to the air electrode 230 through a load (not shown) connecting the fuel electrode 220 with the air electrode 230. Simultaneously, while the air flows in the open groove, electrochemical reduction reaction occurs on the air electrode 230 of the MEA contacted to the open groove 120, hydrogen ion is combined with oxygen, and accordingly water, heat of reaction and additional byproducts are generated. By continuing that process, electrons are moved from the anode (fuel electrode) to the cathode (air electrode) through a load, and electric energy is generated.
The fuel electrode 220 and the air electrode 230 of the fuel cell on which oxidation and reduction reaction occur are generally constructed as a catalyst electrode having a catalyst for activating reaction.
Reference numeral 300 is a collector plate.
FIG. 3 illustrates a MEA of a fuel cell in accordance with the conventional art. As depicted in FIG. 3, in the MEA of the fuel cell, a catalytic layer 221, 231 is respectively coated on both sides of the electrolyte membrane 210 having a certain thickness and a rectangular area, and a coating layer 222, 232 is respectively coated onto the catalytic layer 221, 231. The catalytic layer 221 and the coating layer 222 formed on a side of the electrolyte membrane 210 construct a fuel electrode, and the catalytic layer 231 and the coating layer 232 formed on the other side of the electrolyte membrane 210 construct the air electrode.
In that structure, when fuel and air flow through the open grooves 110, 120 respectively, while oxidation and reduction reaction occur on the fuel electrode 220 and the air electrode 230 of the MEA, reaction of fuel is activated by catalytic reaction of the catalytic layer 221, and hydrogen ions are moved to the air electrode 230 through the electrolyte membrane 210. Herein, when fuel in which hydrogen forming agent such as NaBH4, KBH4, LiAlH4, KH and NaH, etc. is dissolved in an alkali aqueous solution is used, because the fuel is an electrolyte solution, electrons generated with hydrogen ions are moved to the air electrode 230 through the electrolyte solution and the bipolar plate 100.
However, in the conventional structure, when hydrogen ions generated by catalytic reaction by the catalytic layer 221 of the fuel electrode 220 move to the air electrode 230 through the coating layer 222, the catalytic layer 221 and the electrolyte membrane 210, because the catalytic layer 221 of the fuel electrode 220 is coated onto the electrolyte membrane 210, the coated catalytic layer 221 disturbs movement of hydrogen ions toward to the air electrode 230 through the electrolyte membrane 210, ionic action (catalytic action) is active only on a side of the catalytic layer 221, on the contrary, ionic action does not occur on a side contacted to the electrolyte membrane 210, and accordingly current generating efficiency is lowered.